1. Field of the Invention
The present invention relates to a solid-state imaging device furnished with a single-layer color filter having a microlens, and a method of manufacturing the same.
2. Prior Art
As a method of fabricating a color solid-state imaging device, recently, the method of forming a color filter directly on a substrate on which the solid-state imaging device is in the mainstream. In a smaller solid-state imaging device, a microlens is formed on a color filter, and the incident light is focused on the light sensing part through the microlens so as to enhance the light sensing sensitivity.
A conventional solid-state imaging device and its manufacturing method are described herein while referring to the drawings. FIG. 17 is a partial cross section showing the constitution of a conventional solid-state imaging device. FIGS. 18 to 31 are partial cross sections showing the method of manufacturing a conventional solid-state imaging device shown in FIG. 17 in the sequence of processes.
First in FIG. 17, the constitution of a conventional solid-state imaging device is explained.
Plural (e.g. four in FIG. 17) transparent resin layers 2 are formed in order to planarize the surface asperities of a solid-state imaging device substrate 1. Above a light sensing part 3 , a first color filter layer 4, a second color filter layer 5 and a third color filter layer 6 are formed. Further, a microlens 7 is formed above each light sensing part 3. In other words, the transparent resin layers 2 are formed between the light sensing part 3 and the first color filter layer 4, the second color filter layer 5, the third color filter layer 6 and the microlens 7 respectively so as to prevent mixture of colors and to planarize the first color filter layer 4, second color filter layer 5 and third color filter layer 6. In this constitution, the solid-state imaging device having a color filter is realized.
Its operation is as follows.
The light entering the microlens 7 in the uppermost layer is focused, and is separated into lights having spectral transmissivity characteristics individually by the first color filter layer 4, second color filter layer 5 and third color filter layer 6. The separated lights enter the light sensing part 3 beneath each color filter layer. The lights entering the light sensing part 3 are converted into electric signals, and therefore the solid-state imaging device functions to present color pictorial images.
In FIGS. 18 to 31, a manufacturing method of a conventional solid-state imaging device is described.
FIG. 18 shows the state of planarizing the surface by forming the transparent resin layer 2 on the solid-state imaging device substrate 1.
FIG. 19 shows the state of forming a dye base material layer 8 using a dye base material adding a photosensitizer containing chromium (VI) to gelatin, casein or the like. In succession, FIG. 20 shows the state of forming a patterned dye base layer 9. As shown in FIG. 19, the patterned dye base layer 9 is formed by exposing dye base material layer 8 using a mask and then developing and rinsing the dye base material layer 8. FIG. 21 shows the state of forming the first color filter layer 4 by dyeing the patterned dye base layer 9 by using a first dye solution.
FIG. 22 shows the state of forming the transparent resin layer 2 on the first color filter layer 4 for the purpose of planarizing the surface asperities of the first color filter layer 4 and preventing the mixture of colors in the subsequent dye process. FIG. 23 shows the state of forming the dye base material layer 8 similarly as in FIG. 19. FIG. 24 shows the state of forming the patterned dye base layer 9. The patterned dye base layer 9 is also formed by an exposure process using a mask and then developing and rinsing the dye base material layer 8 shown in FIG. 23. FIG. 25 shows the state of forming the second color filter layer 5 by dyeing the patterned dye base layer 9 by using a second dye solution.
FIG. 26 shows the state of forming the transparent resin layer 2 on the second color filter layer 5 for the purpose of planarizing the surface asperities of the second color filter layer 5 and preventing the mixture of colors in the subsequent dye process. FIG. 27 shows the state of forming. the dye base material layer 8 similarly as in FIG. 23. FIG. 28 shows the state of forming the patterned dye base layer 9. The patterned dye base layer 9 is formed by an exposure process using a mask and then developing and rinsing the dye base material layer 8 shown in FIG. 27. FIG. 29 shows the state of forming the third color filter layer 6 by dyeing the patterned dye base layer 9 by using a third dye solution.
FIG. 30 shows the state of forming the transparent resin layer 2 on the third color filter layer 6 for the purpose of planarizing the surface asperities of the third color filter layer 6.
FIG. 31 finally shows the state of forming the microlens 7 by patterning the photosensitive material and treating the material by heating or the like.
The conventional constitution of the solid-state imaging device has a multilayer constitution having plural transparent resin layers 2 formed between adjacent color filter layers 4-6. The conventional solid-state imaging device is accordingly weak to thermal impact from outside, and is limited in reliability. In addition, as the distance between each color filter layer and light sensing part 3 becomes longer, flicker and other defects occur in the image characteristics. Further, since the color filter layers are formed in steps, some of the incident lights run through color filter layers, and unseparated lights enter to cause defects such as white-out and white blemish in the image characteristics. The white-out means that the white point occurs on the color pictorial image. The white-out happens when non separated lights enter the light sensing part 3. Moreover, since the distance from the microlens 7 to the light sensing part 3 is long, the focusing efficiency becomes poor, and the improvement of light sensitivity of the light sensing part 3 is limited.
In the conventional manufacturing method of the solid-state imaging device, the dye base material adding a photosensitizer containing chromium (VI) to gelatin, casein or the like is used, which causes the problem of contamination by chromium. By repeating, still further, the steps of forming and dyeing the dye base layer by using the dye base material to form the first color filter layer 4, second color filter layer 5 and third color filter layer 6, many process steps are desirable to form the solid-state imaging device. Further, although the conventional manufacturing method includes the dyeing process, the conventional method causes the problems of swelling of the color filter layer pattern. As a result, the pattern dimensions are changed before and after dyeing. In the dyeing process, the dyeing occurs while a plurality of significant dyeing conditions are strictly controlled. These dyeing conditions include dye solution temperature, concentration, pH, dyeing time and dyeing fluctuations.
The invention intends to solve the above problems of the prior art. The distance from the color filter layers to the light sensing part is minimized, and the color filter layers are not mutually different in steps. As a result, a solid-state imaging device presenting excellent image characteristics is realized. It is also an object of the invention to present a manufacturing method free from chromium contamination during the dyeing process.